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Citrus growers are not easy because there are more than a dozen light pests and diseases all year round. If you want to rank them, it is the pygmy lice that make the growers feel frightened, because the yellow dragon disease it causes will destroy the entire orchard if it occurs.
In addition to the psyllid, the second place to belong to the citrus red spider, it is the most difficult insect pest in legend, some areas spray up to 30 times a year, if the control is not in place, the disaster of falling leaves, flowers and fruits will follow, directly affecting citrus production. You can imagine how unfathomable the power of the red spider is!
Although it is like facing a great enemy, since the war has started, we must fight to the end, and we should follow the "know thyself and know the other" in the "Art of War" of Sun Tzu, so that we can win every battle." Therefore, today we will take a comprehensive look at the symptoms of red spiders, the occurrence of laws, and what are the prevention and control methods.
1. Symptoms of onset
Many people regard red spiders as insects, and you should know that people belong to the true full eye, leaf mite family, full claw mite genus. In addition to harming citrus, it can also harm yellow peel, peach, persimmon, apple, grape, walnut, jujube, etc., mainly with adult mites, young mites, mites clustered on citrus leaves, young shoots, peels to suck sap, thereby causing leaf fall, fruit fall.
In particular, the damage to the leaves is the most serious, the leaves that have been harmed by the red spider are grayish white and lose their luster, and the normal leaves are green and shiny. Therefore, when you inspect the orchard, you must pay attention to the color of the leaves, once you find the off-white, do not be soft, immediately spray medicine!
If it is a red spider during the bud stage, the leaves cannot be properly expanded, and the leaves become small and thin, resulting in weakened photosynthesis. In the spring, the buds can not open and pollinate normally, which will cause a large number of flowers to fall, fall fruit, and eventually reduce production.
2. Influencing factors
Factors influencing the occurrence of citrus red spiders are climate (temperature, humidity), tree nutrition, overwintering base and natural enemies, of which climate is crucial.
climate
You know, the summer heat is very unfavorable to the growth and reproduction of red spiders. When the temperature exceeds 30 degrees, its development will be affected or even die; if the temperature is suitable, the rainfall is 30 mm, and the red spider base will drop to 45%-70%, which means that the rain can kill a large part of the red spider. However, the wash effect of rain on the eggs of red spiders is very small, because the eggs are laid under the veins on the back of the leaves and are difficult to be washed away.
Tree nutrition
The distribution of the citrus red spider shifts with the twitching of the branches. Spring is first on the autumn shoots, then transferred to the summer shoots, and then the autumn shoots, because the newly extracted branches and leaves have good nutritional conditions, and the female mites that feed on the young leaves tend to produce much more eggs than on the old leaves.
Overwintering base
Spring is a critical period for citrus production, whether it is spring shoots or flower buds, need nutrient supply, if the nutrition is not enough, it will lead to a large number of bud deformities, which is not conducive to fruit forming. The overwintering base of the red spider directly affects the spring production, if the overwintering, each leaf of the red spider more than 1, the next year the red spider is likely to erupt.
natural enemies
There are still many natural enemies of citrus red spiders, such as ladybugs, predatory mites, predatory thrips, grasshoppers and so on. Emphasis is placed on predatory mites, which are mites that eat red spiders. In the process of hunting mites, the pollen of thistle can not be lacking, so the orchard can be a variety of some thistles weeds to reduce the harm of red spiders.
With the irrational use of chemical pesticides, resulting in the death of a large number of natural enemies, in some places the number of red spiders in the prevention and control of up to 20-30 times a year, that is, the biological balance has been destroyed, resulting in more and more serious drugging, so we can consider protecting its natural enemies when controlling.
Just as we know, the occurrence conditions of citrus red spiders are mainly affected by climate, usually the average annual temperature is about 18 degrees, about 16-17 generations a year; the average annual temperature reaches 20 degrees, more than 20 generations a year; the most suitable temperature is 20-25 degrees, often up to 20-30 generations. There are two peak periods for citrus red spiders to occur throughout the year, which are April-June and September-December.
The biggest impact on citrus red spiders is artificial medication, if you take turns using the same drug each time, it will cause red spider resistance, and there will be a multi-peak state throughout the year.
So, what are the developmental generations of citrus red spiders?
Like females, there are 5 insect states: egg stage, larval stage, early nymph, late nymph, and adult worm. Breeding is about 16-22 generations a year, with significant generational overlap. That is, its grandfather may appear at the same time as the grandson.
The number of generations is proportional to the level of temperature, the temperature is high, the generation time is short, and it takes an average of about 16 days for an generation. When the temperature is 25 degrees Celsius and the relative humidity is 85%, the egg stage needs to hatch after 6.5 days, the larval stage takes 2.5 days, the early nymph 2.5 days, the late nymph 3 days, and the adult mite lays about 1.5 days before spawning, which means that the egg stage to the larval stage takes about 9 days.
Citrus red spiders are mostly hermaphroditic, and a female adult mite can lay 30-60 eggs in her lifetime, which shows that the number of breeding bases is as large.
Understand the harmful symptoms and occurrence of red spiders, how to prevent it? First of all, we must choose the right agent, which is divided into mites and egg killers.
Commonly used acaricides are: alkyne mite, pyridoxine, triazoltin, biformamidine, monomericamidine, avermectin, avermectin, azolfal ester, spironite ester;
Oviculicides: tetraamazine, ethanazole.
Note that each acaricide should not be used more than 3 times a year. For example, I used spironate this time, and used azole mite ester when I sprayed it next time; in the summer, you can choose egg killers such as ethanazole and tetramethazine + mites to mix together.
In the actual prevention and control process, we have summarized 1 experience, which can be used in the method of returning to the carbine. That is to say, 7 days after the first spray, spray again, the choice of agents is different between the two times.
Why do you want to do this? We know that it takes about 9 days from the egg stage to the larval stage. The first spray, adult mites can be killed, before killing, adult mites have spawned, eggs to hatch into juvenile mites after 6.5 days, this time the protection of juvenile mites is the weakest, we can choose some economical sprays, you can kill them all.
Therefore, this method can lengthen the control time of red spiders. Finally, with the citrus red spider control formula, for reference only:
Spironite 3000 times + avermectin 2000 times, triazol tin 1500 times, acetazole 2000 times + azole ester 1500 times, biphenylhydrazine 3000 times + pyridoxine 1000 times, tetrapyrazine 1500 times + avermectin 2000 times, spironium ethyl ester 3000 times + azole ester 1500 times, etc.
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